NEW YORK — Prominent planners and builders say now is the time to think big to shield the core of New York City from the next powerful storm like Hurricane Sandy.
Among the projects being suggested are a 5-mile barrier blocking the entryway to New York Harbor and an archipelago of man-made islets guarding the tip of Manhattan.
CDM Smith engineer Larry Murphy envisions a 1,700-foot barrier — complete with locks for passing boats and a walkway for pedestrians — at the mouth of the Arthur Kill waterway between the borough of Staten Island and New Jersey.
If the city acts now, before the next deluge, it could save money in the long run, the planners say.
The strategies aren’t just pipe dreams. Not only do these technologies already exist, some of the concepts have been around for decades and have been deployed successfully in other countries and US cities.
Although the frequency and severity of more killer floods is considered inevitable, Sandy’s 43 deaths and estimated $26 billion in damages citywide might not be enough to galvanize the public and the politicians into action. ‘‘Unfortunately, they probably won’t do anything until something bad happens,’’ said Murphy. ‘‘And I don’t know if this will be considered bad enough.’’
By the end of the century, researchers forecast sea levels will be up to 4 feet higher, producing storm flooding akin to Sandy’s as often as several times each decade. Even at current sea levels, Sandy’s flood waters filled subways, tunnels, and streets in Manhattan.
Without other measures, rebuilding will simply augment the future destruction. Yet that’s what political leaders are emphasizing. President Obama has promised to stand with the city ‘‘until the rebuilding is complete.’’
The focus on rebuilding irks people like Robert Trentlyon, a retired weekly newspaper publisher in lower Manhattan who is campaigning for sea barriers to protect the city: ‘‘The public is at the woe-is-me stage, rather than how-do-we-prevent-this-in-the-future stage.’’
He belongs to a coterie of professionals and ordinary New Yorkers who want to take stronger action. Though pushing for a regional plan, they are especially intent on keeping Manhattan dry.
The 13-mile-long island serves as the country’s financial and entertainment nerve center. Within a 3-mile-long horseshoe-shaped flood zone around its southernmost quadrant are almost 500,000 residents and 300,000 jobs.
A handful of seaside New England cities including New Bedford have built smaller barriers after their own disasters.
However, New York City, which mostly lies just several feet above sea level, has so far escaped the horrors visited elsewhere, so its leaders have been brushing off warnings for years.
Proven technology already exists to blunt or virtually block wind-whipped seas from overtaking lower Manhattan and much of the rest of New York City, according to interviews with engineers, architects and scientists and a review of research on flooding issues in the New York metropolitan area and around the globe.
These strategies range from hard structures like mammoth barriers equipped with ship gates and embedded at entrances to the harbor, to softer and greener shoreline restraints like man-made marshes and barrier islands.